It looks more to me like they're inviting themselves to be robbed when they're not home.

Yeah, I should've thought of that angle.

That sign could also be construed as saying "criminals, you might be able to steal guns from this house when I'm not home," and it makes me wonder if this house is in a jurisdiction which requires firearms to be locked away when stored (No, this isn't me parroting "hippie gun control BS").

Studies show that criminals prefer unarmed victims. I am sure there is some risk to having your weapons stolen - but then again, it's been MY experience that most criminals are generally cowardly, lazy, and opportunistic. And if the house next door has no alarm, no dog, and leave no signs that anyone might be home...it appears to be an easy choice.

BTW I think that is an awesome sign. I have actually used that kind of reasoning with peace loving hippies who shudder at the thought of me carrying a weapon or owning one for that matter. I generally refer them to Lt Col Grossman's article Sheep, Wolves, and Sheepdogs.

it's been MY experience that most criminals are generally cowardly, lazy, and opportunistic.

I never realized the extent to which it is possible for a human being to be impulsive and not think about the future until I started encountering and interacting with drug dealers and their families as part of my job.